Thermostats Designed to Fail Open

[mboucher70 at hotmail.com]

Seven years ago I replaced my thermostat with one of those designed to fail
open.  The brand is Motorad.  Absolutely no complaints.

A bit of context...I'd driven my old audi 100 to hell and back while living
in California.  We'd done the drive from the lowest point in continental USA
(badwater in Death Valley) exiting through the west entrance which climbs
7000 feet in a few miles...This with a family of 5, trunk stuffed with
luggage, A/C on full (its hot in Death Valley), pedal to the floor for much
of the drive.

Later, I'd driven her from California to Montreal.

Point being, I had near absolute confidence in her reliability.  Sure, a
power window switch might act up on occasion, but she would never fail to
get me home.

Then one day, I had a short trip to take...maybe 10 minutes...in the city.
After a few minutes, out of the blue, the temperature warning light flashes
on and I notice that the temperature gauge is way up.  Luckily I could pull
over, let it cool down for 1/2 hour, then make two 5 minute drives to get
her home.

Needless to say, this shook my (over) confidence in the reliability of the
car.  A thermostat always seemed such a simple thing.  Coolant temperature
causes different metals in the thermostat to expand at different rates, and
thus the thermostat opens and water flows.  In the scheme of things, it
would seem one of the least likely devices to abruptly fail.  But experience
shows this isn't the case.

So, given the fact that they can fail at any time and when they do you'll
pretty well have to stop the car within a few minutes or damage the engine,
I opted for the fail-open model.

Searching the audifans archives, I notice that this was discussed in the
past.  Someone mentioned that they'd rather see it fail closed so at least
they know it needs to be fixed.  I appreciate that view.  But I have a
pretty good idea of how long it takes my car to warm up and I think I'd have
a pretty good idea if it was stuck open.  On the other hand, had it failed
driving out of Death Valley while out of cellphone range, even with the
necessary tools, I wouldn't want to be stuck waiting for the engine to cool
down, get the stuck thermostat out, baby crying, girls want to use the
bathroom, and the scorpions and rattlesnakes aren't too far off :-)

My 2cents.

MC

--------------------------------------------------
From: "Kneale Brownson" <kneale at coslink.net>
Sent: Monday, December 13, 2010 12:20 PM
To: <quattro at audifans.com>
Subject: Re: Temp Issue figgered out

> There IS a thermostat designed to fail OPEN so at least you're not
> threatened with overheating.
>
> On 12/13/2010 10:14 AM, Peter Golledge wrote:
>> I think they fail frequently, the last one in the S6 lasted only 3 
>> months!
>>
>> Many of the ones I've replaced with T-belt changes on 200/5000 cars are 
>> failed or failing slightly open (cold).
>>
>> Cheers
>>
>>
>> On 12/12/2010 6:52 PM, Tony Hoffman wrote:
>>> I don't think it's really all that often compared to anything else I 
>>> work
>>> on. I can't tell you the last time I've had to replace one for failing. 
>>> I do
>>> replace them with TB's, but I've had to do the one in the 351C (E-150 
>>> Ford)
>>> at least once every 80k, so that's about the same overall.
>>> Tony
>>>
>>> On Sun, Dec 12, 2010 at 7:04 PM, Nick Lawrence<nick at beol.net>   wrote:
>>>
>>>> So tell me,  why do Audi thermostats fail so often? (At least in my
>>>> opinion)
>>>> Compared to the thermostats in my many Dodge vans?
>>> _______________________________________________
>>> quattro mailing list
>>> http://www.audifans.com/mailman/listinfo/quattro
>>> http://www.audifans.com/kb/List_information
>>>
>> _______________________________________________
>> quattro mailing list
>> http://www.audifans.com/mailman/listinfo/quattro
>> http://www.audifans.com/kb/List_information
>>
> _______________________________________________
> quattro mailing list
> http://www.audifans.com/mailman/listinfo/quattro
> http://www.audifans.com/kb/List_information
>